Restatement of Previously Issued Unaudited Financial Statements - Summary of Table Sets Forth the Effect of Consolidation and Correction of Errors on Condensed Consolidated Statement of Comprehensive Income (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2012
Error Corrections and Prior Period Adjustments Revision [Line Items]
Net income (loss)	$ 20,204	$ 45,941	$ 2,932	$ 32,384	$ 106,586
Comprehensive income	20,252	46,110	3,075		106,918
As Previously Reported [Member]
Error Corrections and Prior Period Adjustments Revision [Line Items]
Net income (loss)	20,859	46,002	51,989		107,073
Comprehensive income	20,907	46,171	52,132		107,405
Consolidation of PEAKS Trust [Member]
Error Corrections and Prior Period Adjustments Revision [Line Items]
Net income (loss)	(1,036)	(61)	(49,607)		(487)
Comprehensive income	(1,036)		(49,607)
Other Adjustments [Member]
Error Corrections and Prior Period Adjustments Revision [Line Items]
Net income (loss)	381	45,941	550		106,586
Comprehensive income	$ 381		$ 550